1. Field of the Invention
This invention is generally related to instruments for performing immunoassays and is specifically directed to an apparatus for performing a selective one of plurality of immunoassays in a single batch of multiple reaction cells.
2. Description of the Prior Art
Biological sample analyzers, of the type considered herein, are automated instruments that may be used in hospitals, clinics, laboratories, or other locations, to run routine tests (assays) on samples of patient specimens such as blood, spinal fluid, urine, serum, plasma, and so on. An automated analyzer of the type discussed herein includes an analyzer unit that runs tests on a number of patient specimen samples that are loaded into the unit. An operator-user prepares the samples by placing portions of the patients, specimen samples into a number of like-sized sample containers. These samples may be diluted or otherwise treated, depending upon the type of analyzer used, the type of assay being performed, and other factors. The containers are then placed in the analyzer unit. The containers may first be placed in a rack or carousel that is then placed in the analyzing unit. The rack may accommodate a number of sample containers, e.g. 24. In addition, one or more appropriate chemical reagents, needed to perform the assays, are also placed in the analyzer unit. In order to mix reagents with the samples, the analyzer unit may also include a fluid moving system, such as a robotic probe mounted on a boom, which is adapted to draw up portions of the reagents and/or samples and expel them into appropriate locations, e.g. additional cells such as reaction cells provided in the sample containers, where a reaction can take place. The analyzer unit also may include a means for detecting a reaction in the reaction cells. This may include an optical detector to observe fluorescence reactions and make optical measurements to obtain a result for each sample. The analyzer unit may also typically include other mechanical systems to move the sample containers and the probe. The analyzer unit may also provide for cleaning the probe between certain tasks in order to avoid contamination between samples. For this purpose, the analyzer unit may also include a washing station and a waste dispensing container to hold the used rinse solution.
After the operator-user loads the specimen samples, enters appropriate instructions, and starts the unit, the analyzer runs unattended. When placed in operation, the analyzer unit, using the appropriate chemical reagent, runs the same test on each of the samples in the sample containers and will perform identical operations on each of the samples loaded in the rack. When it is finished, the analyzer prints out or otherwise reports on the results of its testing.
Biological analyzers utilize different chemistries for performing assays of specimen samples. One type of assays used in biological analyzers includes immunoassays and solid phase procedures. Analyzers for performing immunoassays in general and enzyme immunoassays in particular are known in the art.
A biological analyzer that utilizes immunoassay chemistry to perform assays of specimen samples loaded therein is the IMX.RTM. analyzer introduced in 1988 by Abbott Laboratories, of North Chicago, Ill. (A description of the IMX.RTM. analyzer is included in "The Abbott IMX.RTM. Automated Benchtop Immunochemistry Analyzer System", by Fiore, M. et al, Clinical Chemistry, Vol. 34, No. 9, 1988, which is specifically incorporated herein by reference in its entirety). The IMX.RTM. analyzer is a biological sample analyzer that has been developed for use in conjunction with solid phase immunoassay procedures to perform a variety of assays (such as sandwich and competitive assays). The IMX.RTM. analyzer uses a technology referred to as microparticle capture enzyme immunoassay (MEIA) fluorescence polarization immunoassay (FPIA). The IMX.RTM. analyzer includes a microprocessor used to control a robotic arm with two degrees of freedom and a rotating carousel to process the samples for assay. One assay can be done on each of 24 specimen samples in 30-40 minutes or more unattended after loading (i.e with "walk away" automation). Assay results are output to a printer or a computer interface.
A biological sample analyzer, such as the IMX.RTM. analyzer described above, can execute the steps required for performing assays of up to 24 specimen samples, including the steps of counting the samples, identifying which assay to run, warming the reagents and reaction cells to appropriate temperatures, pipetting the reagents and samples, diluting samples if required, timing critical assay steps such as incubations, washing unbound conjugate, quantifying the fluorescence signal and performing data reduction to yield a useful results.
The container used for holding each of the specimen samples for a biological sample analyzer, such as the IMX.RTM. analyzer, may be a disposable assay cartridge having a plurality of wells, with at least one reaction well and a separation well. The separation well may contain a fibrous matrix positioned across its entrance and an absorbent material positioned below the fibrous matrix. Microparticles react with an analyte containing sample and one or more reagents to form an complex. This complex is immobilized on the matrix of the separation well. The excess sample and reagent are washed through the matrix and captured in the absorbent material below.
The results of the reactions may be read using known optical detection techniques. For example, using conventional solid phase procedures, an analyte can be labeled or tagged with an enzyme which, in the presence of its substrate, fluoresces and emits light at a known wave length. The rate at which the fluorescent product is produced is indicative of the concentration of the analyte in the biological sample. A conventional fluorometer is suitable for illuminating the fibrous matrix with a beam of light having the appropriate excitation wave length. The fluorometer also detects the intensity of the light at the emission wave length assays. Using this type of solid phase technology has been found to provide a high degree of sensitivity.
A biological sample analyzer, such as the IMX.RTM. analyzer, provides for performing assays of patients' specimen samples and reading the results of such assays in a mass production type manner. This allows such assays to be quickly and conveniently available.
Even though such analyzers can provide significant advantages by performing assays quickly and conveniently, further advantages for the user could be obtained if the overall through put of the analyzer could be increased. One way to provide even more advantages and convenience for users of biological analyzers would be to provide the capability to perform more than one assay on the specimen samples in an unattended run. Although a biological analyzer like the IMX.RTM. analyzer can perform different types of assays and can perform assays on a number of specimen samples unattended, the analyzer can run only one type of assay at a time. If a different type of assay is to be performed, the analyzer would have to be reloaded with different reagents. Also, because different types of assays may require different amounts of the sample specimen, different amounts of reagents, different processing steps, different incubation times, etc., the analyzer would also be reset at the beginning of the run to perform the new assay. In the case of the IMX.RTM. analyzer, a different memory module may have to be inserted containing the instructions for the analyzer unit for performing the different assay. Thus, even if only a few of several different types of assays needs to be run, the operator-user has to load and run the analyzer for the first type of assay for only a few samples and then reload the analyzer to run the second type of assay on another batch of samples using perhaps different reagents. It is recognized that for many users of the IMX.RTM. analyzer, or other biological sample analyzers, it would be convenient and advantageous to be able to perform more than one type of assay during an unattended run.
The disposable assay cartridges are particularly well suited for use in automated assay preparation and reading equipment. Due to the low amount of radiant energy produced by assays using the fibrous matrix technology, it is imperative in such automated equipment that the assay containing reaction well of each and every cartridge be positioned with a high degree of accuracy in each of three dimensions with respect to the optical reading apparatus in order to ensure that the readings have a repeatable high degree of accuracy.
The cartridges must not only be precisely positioned, they must be effortlessly and transparently positioned by even an unskilled operator with the same high degree of accuracy, in order to reduce the time and cost of each assay. That is, when the assays can be performed and read in a mass production-type manner, the unit cost for such assays decreases. In addition, the assay results can be made available more quickly.
A carousel for carrying a plurality of reaction cells for use in connection with the Abbott IMX.RTM. System is disclosed in U.S. Pat. No. 4,956,148 entitled: "Locking Rack and Disposable Sample Cartridge" issued to C. J. Grandone on Sep. 11, 1990, and assigned to Abbott Laboratories, the assignee of the present invention.
While instrumentation such as the Abbott IMX.RTM. System and the disposable reaction cell used in combination therewith have greatly advanced the art, each immunoassay test performed by the instrument takes approximately 30-40 minutes or more to run.
In many installations and applications, far fewer than 24 reaction cells are used at any one time. Therefore, the total capacity of the instrumentation is not used during a single immunoassay operation. However, the run time for those assays does not appreciably decrease. It has been found that clinical laboratories desire to run a plurality of different immunoassay tests simultaneously in small batch lots. Currently, the only way of doing such multiple assay runs is to run sequentially multiple carousels, usually half empty, through the instrument.